Flashcards in Local Anesthesia Deck (26)
Which is harder to block myelinated or non-myelinated?
Block is proximal to distal for peripheral fibers, so how does it go with core and mantle?
Out of the alpha category which is the easiest to block?
Which is the easiest fiber to block overall?
What are the first signs you see that a spinal/epidural anesthesia is working vs the first signs you see that a peripheral nerve block is working?
-first sign may be lack of proximal muscle coordination
What type of states of the voltage gated ion channels do local anesthetics prefer to bind?
-inactivated and open rather than resting
Where do local anesthetics bind?
What type of anesthetics can cross the membrane what type can bind the active site?
What determines onset time?
pH and pKa
What determines potency?
What determines duration?
-local tissue proteins-can bind create a sink that slowly released into the nerve-more binding longer they will last
How can you change onset time?
raise the pH of the solution by adding sodium bicarbonate
-use a drug with a lower pKa
What types of drugs is the vasoconstricting power of epinephrine most useful for?
Drugs not highly protein bound like:
What types of drugs is the vasoconstricting power of epinephrine less useful for?
Highly protein bound drugs
What can IV lidocaine treat?
Where do you give spinal anesthesia?
-drug deposited around cauda equina
What level do you give epidural?
-volume dependent segmental blockade
-concentration effects blook quality
-site of action is nerve roots
-not inside dura
How does a blockade of thoracic level affect breathing?
-tidal volume normal
-minimal reduction in vital capacity with abdominal paralysis
-loss of proprioception can be upsetting to patient
If there was respiratory arrest with a high spinal block what would be the cause, what would you do?
-hypoperfusion of respiratory center in the 4th ventricle
-NEVER because of paralyzed phrenic nerves
treat with vasopressors and supportive ventilation
How do neuraxial anesthetics affect vascular beds?
What happens to the heart during neuraxial anesthesia?
brady-unopposed vagal stimulation-decreased venous return-bezold-jarisch reflex
-cardioaccelerator fibers: t1-4 blocked
What does absorption of the drug depend on?
-properties of the drug
-properties of the patient
*renal-increased blood flow-increased absorption
*more acidotic more unchanged so more easily absorbed
Which is more easily affected neuro or cardio?
WHat do you do to treat cardiac toxicity with use of local anesthetic?
-creates a sink that LA can be sequestered into
What is a post dural puncture headache?
-frontal or occipital
-may have neurological deficits
fluid, analgesics, caffeine, blood patch